Glass-to-metal seal

ABSTRACT

A metal member is hermetically sealed to the surface of a wall of a glass member or article such as a reflector portion for a sealed beam automobile headlight lamp. The metal member preferably supports an electrical lead-in conductor which is inserted through a passage embodied in a wall of the glass article for the purpose, for example, of making an electrical connection to an electrical component such as a filament used in a completed headlight lamp using the glass article. The hermetic seal is made between the surface of the glass member which surrounds the passage and a surface of the metal member which is positioned adjacent the glass surface surrounding the passage. In making the hermetic seal, the surface of the glass surrounding the passage is metallized by providing it with an annulus or band of silver paint or other solderable, hermetic and adherent material having a precious metal content and, therefore, having a relatively high temperature coefficient of thermal expansion. The band or annulus and the surface of the metal member facing the annulus are tinned with solder and are then soldered to each other. By using, for the metal member, a material having a relatively low coefficient of thermal expansion, the relatively high expansion silver paint-solder combination is compensated for and a thermal shock resistant glass-to-metal seal results. In a modified form of the invention, the metal member is provided with an orifice or passage for purpose of exhausting a complete lamp.

1' tent ,lan.7, 1975 GLASS-TO-METAL SEAL [75] Inventors: Richard E. Allen, Corning; John F.

, Frazier, Painted Post; William C.

Smith, Corning, all of [73] Assignee: Corning Glass Works, Corning,

[22] Filed: Mar. 29, 1972 [21] Appl. No.2 239,106

[56] References Cited UNITED STATES PATENTS 1,562,533 11/1925 Weintraub 52/759 X 2,163,409 6/1939 Pulfrich 287/189365 2,175,916 10/1939 Pulfrich 52/759 X 2,335,376 ll/1943 Ballintine et al 52/759 X. 2,449,759 9/1948 Braschdorf 287/189.365 2,508,063 5/1950 Gross 240/41 S B 2,569,665 10/1951 Gosling 403/270 X 2,651,144 9/1953 Foley ct al.....' 403/28 X 2,663,812 12/1953 Jamison et al... 403/270 X 2,707,850 5/1955 Dalton et al. 161/196 X 2,756,361 7/1956 Germeshausen. 403/271 X 2,951,167 8/1960 Kegg et a1 161/196 X 3,302,961 2/1967 Franklin 403/272 Primary Examiner-Jordan Franklin Assistant Examiner--Wayne L. Shedd Attorney, Agent, or Firm-Chatles W. Gregg; Clarence R. Patty, Jr.

[57] ABSTRACT A metal member is, hermetically sealed to the surface of a wall of a glass member or article such as a reflector portion for a sealed beam automobile headlight lamp. The metal member preferably supports an electrical lead-in conductor which is inserted through a passage embodied in a wall of the glass article for the purpose, for example, of making an electrical connection to an electrical component: such as a filament used in a completed headlight lamp using the glass article. The hermetic seal is made between the surface of the glass member which surrounds the passage and a surface of the metal member which is positioned adjacent the glass surface surrounding the passage. in making the hermetic seal, the surface of the glass sur rounding the passage is metallized by providing it with an annulus or band of silver paint or other solderable, hermetic and adherent material] having a precious metal content and, therefore, having a relatively high temperature coefficient of thermal expansion. The band or annulus and the surface of the metal member facing the annulus are tinned with solder and are then soldered to each other. By using, for the metal member, a material having a relatively low coefficient of thermal expansion, the relatively high expansion silver paint-solder combination is compensated for and a thermal shock resistant glass-to-metal seal results. in a modified form of the invention, the metal member is provided with an orifice or passage for purpose of ex- I hausting a complete lamp.

2 Claims, 4 Drawing Figures GLASS-TO-METAIL SEAL BACKGROUND OF THE INVENTION In the manufacture of sealed beam automobile headlight lamps, for example, a modification of the so-called Housekeeper hermetic seal has historically been used for providing the lamps with lead-in conductors which extend from outside the lamps to the interior thereof and to which the filaments of the lamps are electrically connected. However, such types of seals are difficult to make and have long been a source of production problems. Furthermore, said type of seal which has been historically used causes optical distortion problems in headlight lamp reflectors since such seals take up a considerable portion of the reflection area of the reflectors of the headlight lamps. More information relative to said so-called Housekeeper seal can be obtained, if such information is desired, by reference to US. Pat. No. 1,293,441 issued Feb. 4, 1919 to W. G. Housekeeper. The use of said modified type of seal in making electric lamps, such as sealed beam headlight lamps, is disclosed, for example, in US. Pat. Nos. 2,148,314; 2,177,216; 2,191,546 and 2,194,373. Reference is made to the modified type of Housekeeper seals shown in FIGS. 1, 3 and 8; FIG. 1; FIG. 1; and FIGS. 2 and 5, respectively, of the above patents taken in the listed order.

For the reasons stated above, a reliable substitution for said seal which has historically been used in the production of sealed beam lamps has long been sought. Furthermore, it has long been felt to be expedient, for economic reasons and for the purpose of providing increased useful reflection area in the reflector portions of sealed beam lamps, to develop a new type of seal which is suitable for achieving said ends and is very satisfactory for the purposes described. Accordingly, the hermetic glass-to-metal seal of the present invention was developed.

It is pointed out that there is disclosed in US. Pat. No. 2,449,759, issued Sept. 21, 1948 to H. O. Barschdorf, a hermetic electrical seal for the end of a ceramic or glass cylinder which may, for example, be used as an enclosure for capacitors, resistors or similar electrical elements. The seal of the Barschdorf patent somewhat resembles some of the embodiments of the seal of the present disclosure but it is believed that the hermetic seal herein specifically disclosed is substantially more thermal shock resistant than that disclosed in said patent. It is, therefore, anobject of the present invention to provide a hermetic glass-to-metal seal which will be substantially more suitable for mass production manufacturing purposes, which is more thermal shock resistant than most hitherto known glass-tometal solder seals and which is more economical than the glass-to-metal seals heretofore used in making sealed beam automobile headlight lamps.

Other objects and characteristic features of the invention will become apparent as the description proceeds.

SUMMARY OF THE INVENTION It is believed that the invention is sufficiently summarized in the abstract of the disclosure previously set forth and, therefore, in order to avoid redundancy and repetition, no brief summary of the invention is given.

BRIEF DESCRIPTION OF THE DRAWINGS In the Drawings;

FIG. 1 comprises an elevational view substntially in cross section and illustrating one form of a hermetical glass-to-metal seal embodying the invention;

FIG. 2 is a view similar to FIG. 1 and illustrating another form of hermetic seal embodying the invention;

FIG. 3 illustrates in cross section still another embodiment of the invention; and

FIG. 4 shows in cross section a fourth embodiment of the invention.

Similar reference characters refer to similar parts in each of the figure of the drawings.

PREFERRED EMBODIMENTS OF THE INVENTION Referring first to FIG. 1 of the drawings in detail, a portion of a wall of a glass article, such as a portion of th back wall 2 of a glass reflector 1 used in making a sealed beam automobile headlight lamp for example, is shown as provided with a passage 2a extending through said back wall 2. Reflector 1 may, for example, be made out of a low expansion type of glass such as PYREX brand glass. Such glass has a coefficient of thernal expansion on the order of 36 X 10 in/in/C in the temperature range of -50 to 500C. A coating, annulus or band 6 of a solderable, hermetic, adherent, and non-oxidizing material having a relatively high temperature coefficient of thermal expansion extends about or surrounds passage 2a in back wall 2 of reflector l. Annulus or band 6 is confined on surface 4 of wall 2 so that it does not extend to the rim of passage 2a and does not extend to the annular rim or edge 7a of a disk-like metal member 7 covering said passage and said annulus, and discussed below. Annulus 6 is provided in order to metallize the portion of the surface surrounding said passage for the purpose of soldering thereto as hereinafter discussed. Annulus 6 may, for example, comprise a hermetic paint having a precious metal content such as silver. For example, a conductive silver composition 7713 which is obtainable from the Electrochemicals Department of duPont, E. 1., de Nemours and Company, Incorporated, Wilmington, Delware may be used for annulus 6. Such paint has a coefficient of thermal expansion of approximately X 10 in/in/C in the temperature range of 0 to 100C.

The previously mentioned metal member 7 shown in FIG. 1 is made of an electrically conductive metal material having a substantially low coefficient of thermal expansion. Such member may, for example, be formed out of a relatively thin plate of Invar 36 material which is obtainable from The Carpenter Technology Company, Reading, Pennsylvania. Such material has a coefficient of thermal expansion on the order of 18 X 10" in/in/C in the temperature range of 18 to +C.

The outer surface of annulus 6 and the facing surface of metal member 7 are tinned with solder. A soldered hermetic seal, as indicated by reference character 8, is provided between said tinned surfaces by using a solder for soldering said surfaces to each other. The solder used for said tinning and soldering of said surfaces may, for example, comprise 50 percent tin, 47 percent lead and 3 percent silver. Such a solder has a coefficient of thermal expansion of approximately 250 X 10' in- /in/C in the temperature range of 0 to 100C. It is believed expedient to point out that the thicknesses of annulus 6 and of solder 8 are, for purposes of ease of illustration and clarity, shown in the drawings on a greatly enlarged or exaggerated scale. This will be readily apparent to those skilled in the art.

Metal member 7 embodies an orifice or passage 7b extending therethrough and an electrical conductor or rod 9 extends through such hole and is hermetically sealed therein as by brazing or soldering the conductor to metal member 7. Conductor or rod 9 also extends through passage 2a in back wall 2 of glass reflector 1 and, when the glass-to-metal seal is used in conjunction with a glass reflector for an automobile headlight lamp, the filaments of such lamp can be connected to conductor 9 for purposes of making electrical connections to such filament.

Referring now to FIG. 2 of the drawings, a portion of a wall of a glass article, such as a portion of the back wall 11 of a glass reflector 10, to be used in making a sealed beam automobile headlight lamp for example, is shown as provided with an annular protuberance or boss 12 which protrudes and minutely tapers outwardly a substantial distance from the exterior surface 14 of back wall 11. A coating or band 16 of a solderable, hermetic and adherent material having a relatively high temperature coefficient of thermal expansion extends about the outer periphery 12a of boss 12. Band or coating 16 is confined on boss 12 so that it does not extend to annular surface 12b of the boss and does not extend to the annular rim or edge 17a of a cap or cap member 17 discussed below. The band or coating 16 is provided on said periphery 12a of boss 12 to metallize the portion of the surface of such periphery covered by said band for the purpose of soldering thereto as hereinafter discussed. The glass material of reflector 10, the material of band 16, and the metal of the material of cap or cap member 17 may, for example, be the same as the materials used for reflector l, annulus 6 and metal member 7, respectively, discussed above in conjunction with the embodiment of FIG. 1 of the drawings.

The above mentioned member 17 may, for example, be formed of swaging or flaring tubes or lengths of tubing of said metal material. If swaging is used there is provided a tube or length of tubing of such material having an inner diameter slightly larger than the diameter of the outer periphery of boss 12 and its surrounding band 16. One end of such tube or tubing is swaged so that a cap or cap member 17 is formed which has a skirt portion 17b which tapers very gradually from the previously mentioned rim or edge 17a of cap or member 17 towards the center region of the tube or length of tubing. In the general region of the center of the tubing or tube, the diameter thereof abruptly diminishes to provide a crown portion 17c on cap or cap member 17 without completely closing the passage through the tube or tubing. One end 19a of a relatively small diameter lead-in conductor or rod 19 of an electrically conductive material, such as a soft iron rod for example, extends concentrically through passage 11a embodied in backwall 11 and in boss 12 provided on such backwall of reflector portion 10, and then through the end of the tube passage at the unswaged end of the tube or tubing and for a short distance into the interior end of the passage extending through the swaged end of the tube or tubing. The swaged end of the tube or tubing is tightly crimped about said end 19a of rod 19 and the remainder of such swaged end is crimped or otherwise compressed to hermetically completely close the passage in the swaged end of the tube or tubing. If considered necessary or desirable to do so, said passage can be further sealed by soldering the swaged end of the tube or tubing where the passage previously opened to the exterior thereof. To assure good electrical connection and firm support of rod 19, cap or cap member 17 is soldered to such rod adjacent end 19a of the rod as indicated by the reference character 20 in FIG. 1.

The outer peripheral surface of band 16 and the inner surface of skirt portion 17b of cap or cap member 17 are tinned with solder. A soldered hermetic seal, as indicated by reference character 18, is provided between said tinned surfaces by using a solder for soldering said surfaces to each other. The solder used for said tinning and soldering may, for example, be identical to that previously described for use in embodiment of FIG. 1 of the invention. It is expedient to point out that the thicknesses of band 16 and of solder 18 are, for purposes of ease of and clarity in illustration, shown in the drawings on a greatly enlarged or exaggerated scale. This, also, will be readily apparent to those skilled in the art.

As previously mentioned, cap or cap member 17 can be made out of a tube or length of tubing by flaring rather than by swaging. In such case, the tube or tubing used for forming cap member 17 is of a relatively small diameter and one end thereof is flared to provide the skirt portion 17a of cap or cap member 17. Following such flaring of the tube or length of tubing, a cap or cap member 17 is formed by using the flared tube or tubing in the manner previously discussed in conjunction with a swaged tube or length of tubing, and is also hermetically sealed to boss 12 in the manner previously discussed for the latter tube or tubing. Furthermore, cap or cap member 17 can be made by a combination of flaring and swaging steps and, in such case, the tube or length of tubing employed would initially be of an intermediate diameter as will be readily apparent to those skilled in the art. A cap or cap member such as 17 can also be readily shaped by other methods and the specific method employed for forming the cap member does not, per se, comprise any part of the present invention.

Referring now to FIGS. 3 and 4 of the drawings, two other forms of glass-to-metal seals embodying the invention are shown and are very similar to that of the second embodiment shown in FIG. 2. The embodiments of the invention shown in FIGS. 3 and 4 will, therefore, be described only briefly.

In the embodiment of FIG. 3, a pressed cap or cap member 22 is used in place of the cap or cap member 17 of FIG. 2. Member 22 is pressed from a material similar or identical to that from which cap or cap member 17 is formed and member 22 comprises a skirt portion 22b similar to skirt portion 17b of cap member 17 and including an annular rim or edge 22a, and a relatively flat crown portion 220 embodying an orifice or hole 22d in the center of the crown and extending therethrough in axial alignment with passage 11a extending through boss 12 and backwall 11 of reflector portion 10. Hole 22d substantially corresponds in diameter with lead-in conductor 19 which extends through such hole and said passage 11a with end 19a of the conductor extending substantially beyond the exterior surface of crown portion 220 of cap 22 for electrical connections to such conductor. Lead-in conductor 19 is brazed to crown portion 22c as indicated by the reference character 23, and conductor 19 and crown portion 22c are thereby hermetically attached to each other. The remainder of the hermetic glass-to-metal seal of the embodiment of FIG. 3 is identical to that described for FIG. 2 and, therefore, for purposes of brevity, a repeated detailed description of such seal will not be given and, in view of the previous description, is not believed necessary for the understanding of those having ordinary skill in the art.

In the embodiment of the invention shown in FIG. 4 a pressed, swaged, flared or otherwise formed cap or cap member 26 includes a skirt portion 26b with an annular rim or edge 26a and a bell-shaped crown portion 26c embodying in the apex of such crown portion an orifice or hole 26d through which end 19a of lead-in conductor 19 snugly extends for a short distance. Conductor 19 is securely fastened in its said position by brazing end 19a of conductor 19 to crown portion 26c of cap or cap member 26 as indicated at 29. A second electrical conductor or terminal 27 is brazed or soldered to the exterior of the end of bell-shaped portion 26c of cap member 26 adjacent said end 19a of lead-in conductor 19. The remainder of the third embodiment of the invention shown in FIG. 4 corresponds to the embodiment shown in FIG. 2 and, therefore, as with the embodiment of FIG. 3, further detailed description of the third embodiment of the invention will be omitted for purposes of conciseness and brevity. However, it is pointed out that bell-shaped portion 260 of cap or cap member 26 embodies a hole 26c which is used for exhausting the completed sealed beam headlight bulb. The need for a central exhaust opening such as 16 shown in FIGS. 1, 2, 4 and 8 of the previously cited US. Pat. NO. 2,148,314, for example, is eliminated by the provision of a hole such as 26:: in the cap or cap member of the present invention. Following the exhausting of the completed bulb through a hole such as 26:2 in a cap or cap member, such hole is, of course, hermetically sealed.

In using materials having coefficients of thermal expansion as herein discussed, it has been found that improved thermal downshock breakage resistance is attained. Such improved resistance is attained, it is thought, although it is not certain, because the substantially low coefficient of thermal expansion of the material of which the member or cap such as 7 is made compensates for the relatively high coefficient of thermal expansion of the combination of the annulus or band such as 6 and of the solder such as 8 employed in the hermetic seal.

It is believed expedient to point out several advantages of the present invention over the hermetic glassto-metal seals of the so-called Housekeeper type previously mentioned and as heretofore being used in the manufacture of sealed-beam automobile headlight lamps.

l. A relatively simple soldering seal operation is substituted for a rather difficult operation of metal insertion into hot glass.

2. The holes in headlight reflectors using the present 6 invention can be made considerably smaller than heretofore provided in such reflectors and, therefore, there will be less optical distortion from the reflectors.

3. Because said holes can be made smaller, if they are embodied in bosses, such bosses can also be correpsondingly smaller and, therefore, there will be less distortion of the glass reflecting area of the reflectors during press forming thereof.

4. Distorti0n of the glass reflecting area of the reflectors due to use of the so-called Housekeeper type of seal will be eliminated.

Other advantages of the hermetic glass-to-metal seal herein disclosed will be readily apparent to those skilled in the art.

Although there is herein shown and described only four embodiments of the invention disclosed, it will be understood that various changes and modifications may be made therein within the purview of the appended claims without departing from the spirit and scope thereof.

We claim:

1. A hermetic glass-to-metal seal between a circular glass boss or protuberance extending outwardly from a wall of a glass article and a complementary metal member, the glass of said article having a coefficient of thermal expansion of about 36 X 10 in/in/C in the temperature range of 50 to 500C and said seal compris- A. an annular band of a hermetic and adherent precious metal paint surrounding the peripheral outer surface of said boss in a central area of such surface removed from the end of the boss and the base thereof where it joins said wall, said boss tapering slightly from said base towards said end thereof and said paint having a coefficient of thermal expansion of about I X 10 in/in/C in the temperature range of 0 to I00C;

B. a metal cap member for said boss and band, such member including a tubular skirt portion surrounding such boss and covering said band, and having a taper corresponding to that of the boss and an inner diameter slightly greater than the outer diameter of said band, and a hermetic electrical terminal portion extending from the smaller end of said skirt portion, and the metal of said member having a coefficient of thermal expansion of about 18 X 10 in/in/C in the temperature range of -l8 to 175C; and

C. a hermetic solder between said band and the inner surface of said skirt portion of said cap member, such solder peripherally surrounding said band in a peripheral area thereof lying within the edges of the band and having a coefficient of thermal expan sion of about 250 X 10 in/in/C in the temperature range of 0 to C.

2. A seal in accordance with claim I and in which said glass article is a reflector portion for a sealed beam automobile headlight lamp and said cap member embodies a hole extending therethrough for exhaustion of a lamp embodying the reflector portion. 

1. A hermetic glass-to-metal seal between a circular glass boss or protuberance extending outwardly from a wall of a glass article and a complementary metal member, the glass of said article having a coefficient of thermal expansion of about 36 X 10 7 in/in/*C in the temperature range of -50* to 500*C and said seal comprising; A. an annular band of a hermetic and adherent precious metal paint surrounding the peripheral outer surface of said boss in a central area of such surface removed from the end of the boss and the base thereof where it joins said wall, said boss tapering slightly from said base towards said end thereof and said paint having a coefficient of thermal expansion of about 170 X 10 7 in/in/*C in the temperature range of 0* to 100*C; B. a metal cap member for said boss and band, such member including a tubular skirt portion surrounding such boss and covering said band, and having a taper corresponding to that of the boss and an inner diameter slightly greater than the outer diameter of said band, and a hermetic electrical terminal portion extending from the smaller end of said skirt portion, and the metal of said member having a coefficient of thermal expansion of about 18 X 10 7 in/in/*C in the temperature range of -18 to 175*C; and C. a hermetic solder between said band and the inner surface of said skirt portion of said cap member, such solder peripherally surrounding said band in a peripheral area thereof lying within the edges of the band and having a coefficient of thermal expansion of about 250 X 10 7 in/in/*C in the temperature range of 0* to 100*C.
 2. A seal in accordance with claim 1 and in which said glass article is a reflector portion for a sealed beam automobile headlight lamp and said cap member embodies a hole extending therethrough for exhaustion of a lamp embodying the reflector portion. 